A TYPHOON is a mature tropical cyclone that develops in the western
part of the
North Pacific Ocean between 180° and 100°E . This region
is referred to as the Northwestern Pacific Basin , and is the most
active tropical cyclone basin on
Earth , accounting for almost
one-third of the world's annual tropical cyclones. For organizational
purposes, the northern
Pacific Ocean is divided into three regions:
the eastern (North America to 140°W ), central (140° to 180°W), and
western (180° to 100°E). The Regional Specialized Meteorological
Center (RSMC) for tropical cyclone forecasts is in
Japan , with other
tropical cyclone warning centers for the northwest Pacific in Hawaii
Joint Typhoon Warning Center ), the
Hong Kong .
While the RSMC names each system, the main name list itself is
coordinated among 18 countries that have territories threatened by
typhoons each year. Only the
Philippines use their own naming list for
systems approaching the country.
A typhoon differs from a cyclone or hurricane only on the basis of
location. A hurricane is a storm that occurs in the Atlantic Ocean
Pacific Ocean , a typhoon occurs in the northwestern
Pacific Ocean, and a cyclone occurs in the south Pacific or Indian
Within the northwestern Pacific there are no official typhoon seasons
as tropical cyclones form throughout the year. Like any tropical
cyclone, there are six main requirements for typhoon formation and
development: sufficiently warm sea surface temperatures , atmospheric
instability, high humidity in the lower to middle levels of the
Coriolis force to develop a low pressure center ,
a pre-existing low level focus or disturbance, and low vertical wind
shear . While the majority of storms form between June and November, a
few storms do occur between December and May (although tropical
cyclone formation is at a minimum during that time). On average, the
northwestern Pacific features the most numerous and intense tropical
cyclones globally. Like other basins, they are steered by the
subtropical ridge towards the west or northwest, with some systems
recurving near and east of
Japan . The
Philippines receive the brunt
of the landfalls, with
Japan being impacted slightly less.
Some of the deadliest typhoons in history have struck China. Southern
China has the longest record of typhoon impacts for the region, with a
thousand-year sample via documents within their archives.
received the wettest known typhoon on record for the northwest Pacific
tropical cyclone basins .
* 1 Nomenclature
* 1.1 Etymology and usage
* 1.2 Intensity classifications
* 2 Genesis
* 3 Frequency
* 4 Paths
* 5 Basin monitoring
* 5.1 Name sources
* 6 Records
* 7 See also
* 8 References
* 9 External links
ETYMOLOGY AND USAGE
The term typhoon is the regional name in the northwest Pacific for a
severe (or mature) tropical cyclone , whereas hurricane is the
regional term in the northeast Pacific and northern Atlantic.
Elsewhere this is called a tropical cyclone, severe tropical cyclone,
or severe cyclonic storm.
Oxford English Dictionary cites
Urdu ṭūfān and Chinese tai
fung giving rise to several early forms in English. The earliest forms
-- "touffon", later "tufan", "tuffon", and others -- derive from Urdu
ṭūfān, with citations as early as 1588. From 1699 appears
"tuffoon", later "tiffoon", derived from Chinese with spelling
influenced by the older Urdu-derived forms. The modern spelling
"typhoon" dates to 1820, preceded by "tay-fun" in 1771 and "ty-foong",
all derived from the Chinese tai fung.
Urdu source word توفان ṭūfān ("violent storm"; cognate
Hindi तूफ़ान (tūfān)) comes via Persian from Arabic
طوفان (ṭūfān), which may derive from the verb tūfīdan
(Persian : توفیدن/طوفیدن, "to roar, to blow
furiously") or Arabic ṭāfa, to turn round.
The Chinese source is the word tai fung (simplified Chinese :
台风; traditional Chinese : 颱風; pinyin : táifēng), cited as a
common dialect form of Mandarin dà "big" and fēng "wind". In
Mandarin the word for the windstorm is 大风 (dàfēng, "big wind")
Cantonese 大風 (daai6 fung1, "big wind"). The modern Japanese
word is also derived from Chinese: 台風 (たいふう, taifuu). The
first character in Japanese has a usual modern meaning of "pedestal"
or "stand", but it is actually a simplification of an older kanji 颱
which had a meaning of "typhoon" by itself. So the Japanese characters
originally had a meaning of "typhoon wind".
Ancient Greek Τυφῶν (Tuphôn,
Typhon ) is not unrelated and
has secondarily contaminated the word. The Persian and Chinese terms
may have been originated by the Greek word in the first place.
RSMC TOKYO \'S TROPICAL CYCLONE INTENSITY SCALE
VERY STRONG TYPHOON
SEVERE TROPICAL STORM
Tropical cyclone scales
A tropical depression is the lowest category that the Japan
Meteorological Agency uses and is the term used for a tropical system
that has wind speeds not exceeding 33 knots (38 mph; 61 km/h). A
tropical depression is upgraded to a tropical storm should its
sustained wind speeds exceed 34 knots (39 mph; 63 km/h). Tropical
storms also receive official names from RSMC Tokyo. Should the storm
intensify further and reach sustained wind speeds of 48 knots (55 mph;
89 km/h) then it will be classified as a severe tropical storm. Once
the system's maximum sustained winds reach wind speeds of 64 knots (74
mph; 119 km/h), the JMA will designate the tropical cyclone as a
typhoon—the highest category on its scale.
From 2009 the
Hong Kong Observatory started to further divide
typhoons into three different classifications: typhoon, severe typhoon
and super typhoon. A typhoon has wind speed of 64-79 knots (73-91
mph; 118–149 km/h), a severe typhoon has winds of at least 80 knots
(92 mph; 150 km/h), and a super typhoon has winds of at least 100
knots (120 mph; 190 km/h). The
United States ' Joint
Center (JTWC) unofficially classifies typhoons with wind speeds of at
least 130 knots (67 m/s; 150 mph; 241 km/h)—the equivalent of a
Category 4 storm in the Saffir-Simpson scale —as super
typhoons. However, the maximum sustained wind speed measurements that
the JTWC uses are based on a 1-minute averaging period, akin to the
National Hurricane Center
National Hurricane Center and
Central Pacific Hurricane Center .
As a result, the JTWC's wind reports are higher than JMA's
measurements, as the latter are based on a 10-minute averaging
Depth of 26 °C isotherm on October 1, 2006 See also: Tropical
There are six main requirements for tropical cyclogenesis:
sufficiently warm sea surface temperatures, atmospheric instability,
high humidity in the lower to middle levels of the troposphere ,
Coriolis force to develop a low pressure center, a pre-existing
low level focus or disturbance, and low vertical wind shear. While
these conditions are necessary for tropical cyclone formation, they do
not guarantee that a tropical cyclone will form. Normally, an ocean
temperature of 26.5 °C (79.7 °F) spanning through a depth of at
least 50 metres (160 ft) is considered the minimum to maintain the
special mesocyclone that is the tropical cyclone. These warm waters
are needed to maintain the warm core that fuels tropical systems. A
minimum distance of 500 km (300 mi) from the equator is normally
needed for tropical cyclogenesis.
Whether it be a depression in the Intertropical Convergence Zone
(ITCZ) or monsoon trough , a broad surface front , or an outflow
boundary , a low level feature with sufficient vorticity and
convergence is required to begin tropical cyclogenesis. About 85 to 90
percent of Pacific typhoons form within the monsoon trough. Even with
perfect upper level conditions and the required atmospheric
instability, the lack of a surface focus will prevent the development
of organized convection and a surface low. Vertical wind shear of less
than 10 m/s (20 kn, 33 ft/s) between the ocean surface and the
tropopause is required for tropical cyclone development. Typically
with Pacific typhoons, there are two outflow jets : one to the north
ahead of an upper trough in the
Westerlies , and a second towards the
In general, westerly wind increases associated with the
Madden–Julian oscillation lead to increased tropical cyclogenesis in
all tropical cyclone basins . As the oscillation propagates from west
to east, it leads to an eastward march in tropical cyclogenesis with
time during that hemisphere's summer season. On average, twice per
year twin tropical cyclones will form in the western Pacific Ocean,
5th parallel north and the
5th parallel south , along the
same meridian, or line of longitude. There is an inverse relationship
between tropical cyclone activity in the western Pacific basin and the
north Atlantic basin, however. When one basin is active, the other is
normally quiet, and vice versa. The main reason for this appears to be
the phase of the Madden–Julian oscillation, or MJO, which is
normally in opposite modes between the two basins at any given time.
Tropical storms and Typhoons by month,
for the period 1959–2015 (Northwest Pacific)
Nearly one-third of the world's tropical cyclones form within the
western Pacific. This makes this basin the most active on Earth.
Pacific typhoons have formed year round, with peak months from August
to October. The peak months correspond to that of the Atlantic
hurricane seasons . Along with a high storm frequency, this basin also
features the most globally intense storms on record. One of the most
recent busy seasons was 2013 . Tropical cyclones form in any month of
the year across the northwest Pacific Ocean, and concentrate around
June and November in the northern Indian Ocean. The area just
northeast of the
Philippines is the most active place on
tropical cyclones to exist. Across the
activity reaches a minimum in February, before increasing steadily
through June, and spiking from July through October, with September
being the most active month for tropical cyclones across the
archipelago . Activity falls off significantly in November, although
Typhoon Haiyan , the strongest Philippine typhoon on record, was a
November typhoon. The most frequently impacted areas of the
Philippines by tropical cyclones are northern and central
Visayas . A ten-year average of satellite determined
precipitation showed that at least 30 percent of the annual rainfall
in the northern
Philippines could be traced to tropical cyclones,
while the southern islands receive less than 10 percent of their
annual rainfall from tropical cyclones. The genesis and intensity of
typhoons are also modulated by slow variation of the sea surface
temperature and circulation features following a near-10-year
Hurricane belt Tracks of all tropical cyclones in the
Pacific Ocean between 1980 and 2005. The vertical line
to the right is the
International Date Line
International Date Line .
Most tropical cyclones form on the side of the subtropical ridge
closer to the equator, then move poleward past the ridge axis before
recurving north and northeast into the main belt of the
When the subtropical ridge shifts due to El Niño , so will the
preferred tropical cyclone tracks. Areas west of
to experience many fewer September–November tropical cyclone impacts
during El Niño and neutral years. During El Niño years, the break in
the subtropical ridge tends to lie near 130°E , which would favor the
Japanese archipelago. During La Niña years, the formation of
tropical cyclones, and the subtropical ridge position, shift westward
across the western Pacific Ocean, which increases the landfall threat
China and greater intensity to
Philippines . Those that form near
Marshall Islands find their way to Jeju Island , Korea.
Typhoon paths follow three general directions.
* Straight track (or straight runner). A general westward path
Philippines , southern China,
Taiwan , and
* A parabolic recurving track. Storms recurving affect eastern
Philippines, eastern China, Taiwan, Korea, Japan, and the Russian Far
* Northward track. From point of origin, the storm follows a
northerly direction, only affecting small islands.
A rare few storms, like Hurricane John , were redesignated as
typhoons as they originated in the Eastern/Central Pacific and moved
into the western Pacific.
Within the Western Pacific, RSMC Tokyo-
Typhoon Center , part of the
Japan Meteorological Agency has had the official warning
responsibility for the whole of the Western Pacific since 1989, and
the naming responsibility for systems of tropical storm strength or
greater since 2000. However each National Meteorological and
Hydrological Service within the western Pacific has the responsibility
for issuing warnings for land areas about tropical cyclones affecting
their country, such as the
Joint Typhoon Warning Center for United
States agencies, the Philippine Atmospheric, Geophysical and
Astronomical Services Administration (PAGASA) for interests in the
island archipelago nation, and the
Hong Kong Observatory for storms
that come close enough to cause the issuance of warning signals .
The list of names consists of entries from 17 Southeast and East
Asian nations and the
United States who have territories directly
affected by typhoons. The submitted names are arranged into five
lists, and each list is cycled with each year. Unlike tropical
cyclones in other parts of the world, typhoons are not named after
people. Instead, they generally refer to animals, flowers,
astrological signs, and a few personal names. However, PAGASA retains
its own naming list, which does consist of human names. Therefore, a
typhoon can possibly have two names. Storms that cross the date line
from the central Pacific retain their original name, but the
designation of hurricane becomes typhoon. In Japan, people use the
numerical designation of typhoons according to the sequence of their
occurrence in the calendar year.
The most active Western Pacific typhoon season was in 1964, when 39
storms of tropical storm strength formed. Only 15 seasons had 30 or
more storms developing since reliable records began. The least
activity seen in the northwest
Pacific Ocean was during the 2010
Pacific typhoon season , when only 14 tropical storms and seven
typhoons formed. In the Philippines, the most active season, since
1945, for tropical cyclone strikes was 1993 when nineteen tropical
cyclones moved through the country. There was only one tropical
cyclone that moved through the
Philippines in 1958 . The 2004 Pacific
typhoon season was the busiest for Okinawa since 1957. Within
Guangdong in southern China, during the past thousand years, the most
active decades for typhoon strikes were the 1660s and 1670s.
The highest reliably-estimated maximum sustained winds on record for
a typhoon were those of
Typhoon Haiyan at 195 miles per hour (314
km/h) shortly before its landfall in the central
Philippines on Nov.
8, 2013. The most intense storm based on minimum pressure was Typhoon
Tip in the northwestern
Pacific Ocean in 1979, which reached a minimum
pressure of 870 hectopascals (26 inHg) and maximum sustained wind
speeds of 165 knots (85 m/s, 190 mph, 310 km/h). The deadliest
typhoon of the 20th century was
Typhoon Nina , which killed nearly
China in 1975 due to a flood that caused 12 reservoirs to
Typhoon Morakot landed in
Taiwan at midnight on August 8,
2009, almost the entire southern region of
Taiwan (Chiayi County
Chiayi City ,
Tainan County /
Tainan City (now merged as Tainan),
Kaohsiung County /
Kaohsiung City (now merged as Kaohsiung), and
Pingtung County ) and parts of
Taitung County and
Nantou County were
flooded by record-breaking heavy rain. The rainfall in Pingtung County
reached 2,327 millimeters (91.6 in), breaking all rainfall records of
any single place in
Taiwan induced by a single typhoon, and making
the cyclone the wettest known typhoon.
* Tropical cyclones portal
China tropical cyclone rainfall climatology
Effects of tropical cyclones
* Typhoons in the
2017 Pacific typhoon season
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Hong Kong Observatory
Typhoon Warning Center